1. Technical Field
The present invention relates to an electro-optical device, a driving method thereof and an electronic apparatus having the electro-optical device.
2. Related Art
As an example of an electro-optical device, liquid crystal display devices will be described.
Generally, in liquid crystal display devices of an active matrix type in which a pixel electrode is driven by a thin film transistor (hereinafter, referred to as “TFT”), in order to prevent display problems such as flicker or burn-in of a displayed image, for example, inversion driving (driving by an alternating voltage) where the polarity of a driving voltage applied to each pixel electrode is inverted every frame of an image signal has been employed.
This is for preventing a DC voltage component from being applied to a liquid crystal layer and for resolving display problems such as burn-in by utilizing the inversion driving. However, by simply performing only the inversion driving, the application of a DC voltage component is not completely prevented, and still the display problems occur.
In other words, even when the inversion driving is performed, a DC voltage component is applied to the liquid crystal layer. Accordingly, a countermeasure for the generation sources of this DC voltage component is needed. In addition, as the generation sources of the DC voltage component, the following two phenomena are known of.
First, the first phenomenon is so-called a field-through (also referred to as push-down) phenomenon. The field-through is a phenomenon where the voltage of a pixel electrode connected to the drain terminal of a TFT decreases due to parasitic capacitance between the gate and the drain terminals of the TFT and between the source and drain terminals of the TFT when the TFT is switched from the ON state to the OFF state. In particular, the field-through is a phenomenon of a voltage decrease of the pixel electrode due to the redistribution of electric charges that are stored in the parasitic capacitance and the storage capacitor at the off timing of the TFT.
The second phenomenon is generation of a DC voltage component due to a characteristic difference between a component substrate and an opposing substrate that sandwitches the liquid crystal layer. In particular, this phenomenon is due to asymmetry of electrical characteristics of the component substrate in which a pixel electrode, a TFT, and the like, are formed and the opposing substrate in which a common electrode is formed.
In JP-A-2002-189460, a method of driving a liquid crystal display device has been proposed in consideration of the above-described two phenomena.
In the driving method, it is proposed that a common electrode electric potential which is the reference for the inversion of the polarity in the inversion driving is shifted in advance by a voltage change caused by the field-through and the characteristic difference. In particular, a voltage variation, due to the field-through and the DC voltage component generated by the characteristic difference, is measured on a predetermined measurement condition, and the sum value thereof is added to the set electric potential of the common electrode as a constant correction voltage in the initial setting process.
However, in the typical driving method disclosed in JP-A-2002-189460, there have been difficulties with sufficiently suppressing display problems such as flicker or burn-in of a displayed image. In particular, according to experimental data of the inventors, it is difficult to offset the DC voltage component by a constant correction voltage, because the DC voltage component due to a characteristic difference between a component substrate and an opposing substrate correlates with a driving voltage. In addition, although the correlation ratio is lower than that of the characteristic difference, there is also correlation between the field-through and the driving voltage.
In summary, in a typical liquid crystal display device in which the DC voltage components, due to the above-described two phenomena, are compensated by a constant correction voltage, display problems such as burn-in occur due to the application of the DC voltage component to the liquid crystal layer.